THE AGENIÆ; THE PELOPÆUS’ VICTUALS
Judging only by instincts and habits, a characteristic superior to all
others, we must rank not far below the builder whose nest we have been
considering certain other Wasps of our country-side, Spider-hunters
like the first and, like her, worthy, or perhaps even more worthy, of
the title of Πηλοποιός, a worker in clay or mud, a potter. My district
possesses two of these ceramic artists: Agenia punctum, Panz., and A.
hyalipennis, Zetterstedt.
With all their talent they are very frail creatures, clad in black and
hardly larger than the ordinary Gnat. Their pottery amazes us when we
remember the feebleness of the artisan. It surprises us even more by
its regularity, which may be compared with the product of the
turning-lathe. Adhering broadly to a flat base and leaning one against
the other, the Pelopæus’ cells, in the full elegance of the first
phase, are merely semicylinders whose circular contour is accentuated
only at the mouth; while those of the Ageniæ, which are almost isolated
from one another and take hold of their support only at a restricted
spot, retain from end to end a regular convexity, suggesting the tiny
pots of a miniature set of crockery. If any one deserves the epithet of
spirifex, or turner, it is the Agenia rather than the Pelopæus. No
other manipulator of potter’s clay possesses her dexterity.
The pots of A. punctum are shaped like oval jars, each smaller than a
cherry-stone. Those of A. hyalipennis affect a conoid form, narrow at
the base and wider at the mouth, like the primitive drinking-cup, the
cyathus of the ancients. Both have a polished interior and a very much
granulated exterior, the maker allowing the little mouthful of mortar
which she has brought to project outside, without seeking to level it,
as she does so carefully upon the inner wall. These granulations are
the equivalent of the slanting fillets left by the Pelopæus. No
rough-cast, no plaster is applied to conceal the pretty bit of
earthenware; no reinforcement of casing is added. Such as it was when
the potter moulded the neck, such it remains after it has received its
lid and its little Spider with an egg laid upon her side. The Agenia’s
urns then, notwithstanding their brittleness, are left entirely
unprotected, whether they be placed end to end in a winding row or
grouped in a confused cluster.
Nevertheless, the mother displays a precaution unknown to the Pelopæus.
A drop of water placed inside the latter’s cell quickly spreads and
disappears, soaking the walls. In an Agenia’s cell it remains at the
point touched, without penetrating the thickness. The urn therefore is
glazed on the inner surface, like our ordinary pots, which are made
watertight by the silicate of lead furnished by the potter’s galena.
The waterproofing employed cannot be other than the Agenia’s saliva, an
agent which is anything but plentiful, because of the insect’s exiguous
dimensions, and so it is applied only on the side. Indeed, if I stand a
cell on a drop of water, I see the moisture at once spread from bottom
to top and turn the vessel into pulp, until nothing is left but a thin
inner layer, which is less yielding.
I do not know where the Ageniæ get their materials. Do they follow the
Pelopæus’ custom and collect loam ready prepared, wet earth, mud or
naturally plastic clay; or, copying the method of the Mason-bees, do
they use cement scraped together atom by atom and converted into paste
with the saliva? Direct observation has failed to tell me anything in
this respect. From the colour of the cells, which are now red, like the
soil of our stony expanses, now whitish, like the dust of the highways,
now greyish, like certain chalk-beds in the neighbourhood, I see
plainly that the material for the pots is collected everywhere
indifferently, but I am unable to determine whether, at the actual
moment of collection, it is paste or powder.
I incline, however, to the latter alternative, because of the
impermeable inner surface of the cells. Earth already soaked with
natural moisture would not readily absorb the Agenia’s saliva and could
not acquire the watertight qualities which I find that it possesses.
This peculiarity makes it highly probable that the cement is collected
dry and that the insect mixes it in order to turn it into plastic clay.
Then how are we to explain the outside of the pot, which melts upon
contact with a drop of water, and the inside, which remains intact?
Very simply: for the outside materials the potter uses only the water
with which she slakes her thirst from time to time; for the inside
materials she uses pure saliva, a precious agent which has to be
thriftily employed, so that she may equip her family with a sufficiency
of earthenware. To construct her pots, the Agenia must possess two
separate fluid-reservoirs: the crop, a bottle which is filled with
spring-water; and the gland, a phial in which the watertight chemical
product is sparingly elaborated.
The Pelopæus knows nothing of these scientific methods. To the mud
collected ready-made she adds nothing that develops resisting-powers
later; when attacked by water, her cells quickly become soaked and
allow the moisture to ooze through to the inside. Hence probably, in
her case, the necessity for a thick casing of plaster to protect the
too permeable dwelling. Each potter has her portion: the giantess, the
rough covering of loam; the dwarf, the thin coating of varnish.
Despite their inner glaze, the Agenia’s cells are too readily affected
by water and moreover too fragile to remain exposed to the open air
with impunity. They need a shelter quite as badly as those of the
Pelopæus. This shelter is found in all manner of places, excepting our
houses, where the frail potter very rarely takes refuge. A tiny cavity
under the stump of a tree; a hole in some wall or other, exposed to the
sun; an old Snail-shell under a heap of stones; a Capricorn’s disused
burrow bored in the oak; an Anthophora’s [31] deserted dwelling; a fat
Earth-worm’s mine-shaft opening on a dry bank; the hole whence the
Cicada [32] has emerged: anything, in short, suits her, provided that
the accommodation be sheltered from the rain. Once only did Agenia
punctum, who is more frequent than the other, pay me a visit. She had
established her collection of pots in some little paper bags lying on
the shelves of a green-house and intended to hold seeds. This
nest-building on a sheet of paper reminded me of the Pelopæus confiding
her cells to the books in a distillery or the curtains of a window.
Indifferent to the nature of the support for their nests, both potters
sometimes choose very curious sites.
Now that we know the provision-jar, let us ascertain what it contains.
The Pelopæus’ larvæ are fed on Spiders, a diet likewise dear to the
Ageniæ and to the Pompili. [33] The game does not lack variety, even in
the same nest and the same cell. Any Spider may form part of the
ration, provided that her dimensions do not exceed the capacity of the
jar. My abstracts of victuals mention the following genera: Epeira,
[34] Segestria, Clubionus, [35] Attus, Theridion and Lycosa; [36] and
the list could no doubt be extended, were it worth while to continue
the bill of fare. The Epeiræ are most numerous. Those recurring most
frequently belong to the following species: E. diadema, scalaris,
adianta, pallida and angulata. The Diadem Epeira, or Cross Spider, [37]
with three crosses of white dots on her back, is the dish that occurs
oftenest.
I should hesitate to regard this frequency as indicating a special
predilection of the Pelopæus for this kind of game. In her
hunting-trips the Wasp does not go far from her home; she visits the
old walls near by, the hedges, the little gardens all around and
captures whatever offers. Now in these conditions the Cross Spider
happens, at the nesting-period, to be the commonest. Every reed-fenced
garden-patch in front of the rough cottage beloved by the potter, every
hawthorn-hedge surrounding a cabbage-plot shows me the Spider with the
pontifical cross weaving her net or waiting for her prey in the centre
of her web. If I need a Spider for my studies, I am certain of finding
the Diadem Epeira within a few steps of my house. That much keener
investigator, the Pelopæus, must easily effect this kind of capture;
and this, it seems to me, is the reason why that particular morsel
predominates in the provision-store.
If the Epeira, the habitual foundation of the meal, happen to be
lacking, any other Spider is regarded as adequate, even when she
belongs to a very different group. We have here the wise eclecticism of
the Crabro-wasps [38] and Bembeces, who welcome any member of the Fly
clan, provided that the prey be not disproportionate to the huntress’
strength. We should be wrong, however, to erect this indifference into
too absolute a principle: there is reason to believe that the Pelopæus
recognizes different qualities of nourishment and flavour between one
Spider and another. A more fastidious expert than Lalande, [39] with
his legendary passion for plump, nutty Spiders, she must rate this
species more highly than that; and there are some which she must
absolutely despise. These include the House Spider (Tegenaria
domestica), who weaves her cobwebs in the corners of our houses.
On the kitchen-ceiling and on the rafters of the granary this Spider is
her near neighbour: the silken lair stretches in close proximity to the
earthen nest. Instead of expeditions in the neighbourhood, a little
patrolling of the actual premises where she has settled down would
provide the Pelopæus with abundant sport, for there is game swarming at
her very door. Why does she not profit by this plenty? The dish is not
to her liking; and it would be very difficult to tell the reason why.
The fact remains that, in all my stock-taking of victuals, I have never
found the House Spider among the provisions, although the species, if
captured young, would seem to fulfil the required conditions. This
disdain is a pity both for our sake and for the Pelopæus’; for ours, in
the first place, because we should otherwise possess, inside our
dwellings, an inspector of ceilings whose duty it would be to
exterminate the spinners of cobwebs that cause the housewives such
trouble; next, for the sake of the Pelopæus, who, once inscribed on the
hallowed roll of useful insects, would enjoy an established reputation
and receive a friendly welcome in the farm-house, instead of being
driven out when too lavish with her mud.
The Spider, armed with poison-fangs, is a dangerous quarry to tackle;
when of fair size, she demands of her adversary an audacity and above
all a tactical skill which the Pelopæus, it seems to me, does not fully
possess. Moreover, the small diameter of the cells would not admit a
bulky prey, such as the Tarantula hunted by the Ringed Calicurgus. [40]
The Calicurgus deposits her corpulent victim in a cavern obtained
without labour in the old plaster at the foot of a wall; the Pelopæus
places hers in a jar, a laborious construction whose capacity has to be
reduced to suit the larva. The Pelopæus, therefore, hunts game of
moderate size, smaller than one would at first expect from the insect’s
vigorous appearance. If she encounters a species that is apt to become
plump, she always selects a young one. This happens in the case of the
Cross Spider, who, when full-grown, with her belly swollen with eggs,
almost rivals the Calicurgus’ Tarantula and who is admitted to the
provision-jar only when of niggardly dimensions, very different from
those which maturity will bring. For the rest, the size varies, between
one specimen and another, by a hundred per cent and more. The essential
point is that the quarry can be stored in the narrow jar. This
variation in the size of the items provided leads to corresponding
variations in their number. One cell is stuffed with a dozen Spiders;
another contains only five or six. The average number is eight. The
nurseling’s sex must of a surety play its part, as with the other
Wasps, in regulating the luxuries of the table.
The culminating feature in the biography of any hunting insect is the
method of attack; and so I did my utmost to observe the Pelopæus at
grips with her quarry. My patient waits in front of her favourite
hunting-grounds, old walls and bramble-thickets, were not crowned with
any great success. I have seen the Pelopæus fall suddenly upon the
Spider madly fleeing and clasp and carry off her victim almost without
delaying her flight. The other game-hunters alight on the ground,
solemnly make their fastidious preparations and distribute their
lancet-strokes with the calm deliberation which a delicate operation
demands. The Pelopæus darts forward, seizes her prey and makes off,
very much as the Bembeces do. There is reason to believe, so sudden is
the rape, that she makes use of her sting and her mandibles only during
the flight, on her journey home. This fierce procedure, which is
incompatible with scientific surgery, explains even better than the
narrowness of the cells her preference for Spiders of small dimensions.
A sturdy prey, armed with its two poison-fangs, would constitute a
deadly peril to the ravisher disdainful of precautions. The lack of
artifice calls for a feeble victim. It also makes us suspect that the
Spider so hastily set upon is killed.
Indeed, I have over and over again armed my eyes with a
magnifying-glass and scrutinized the contents of cells whose eggs had
not yet hatched, a proof that the provisions were of recent date: there
is never a quiver of either palpi or tarsi in the victims stored away.
It is only with difficulty that I manage to preserve them: in ten days’
time, more or less, I see them grow mouldy and putrefy. The Spiders,
therefore, are dead, or very nearly so, when they are potted by the
Pelopæus. Is the skilful paralysis which the Calicurgus practises upon
the Tarantula, who keeps fresh for seven weeks, unknown to the
Pelopæus, or is it impracticable in the fierceness of the attack? Are
we, in her case, dealing not with a delicate practitioner, who is able
to abolish movement without destroying life, but rather with a brutal
sacrificer, who, to deprive her victims of their power of movement,
kills them? Everything in their withered aspect and their rapid decay
assures us that this is so.
The evidence does not surprise me: we shall see, as we go on, other
victimarii inflict death instantly with a stroke of the stiletto,
delivered with a science of slaughter no less astonishing than the
science of the paralysers. We shall see the reasons that call for these
complete murders and we shall recognize, under other aspects, the
profound anatomical and physiological knowledge which a rational action
would demand in order to rival the unconscious action of instinct. As
for the necessity of killing her Spiders under which the Pelopæus
labours, I find it impossible even to suspect the cause.
What I do see, without any lengthy investigations, is the logical
method whereby the Pelopæus makes the most of the corpses threatened
with speedy putrefaction. To begin with, each cell contains a number of
victims. The carcase actually attacked by the larva, ground between its
mandibles, abandoned and attacked at another point, soon becomes a
shapeless and disorganized mass, more liable than ever to putrefy. But
it is small and is therefore consumed at a single sitting, before
decomposition overtakes it; for once the larva has bitten into a Spider
it does not turn elsewhere for food. The others therefore remain
intact, which is enough to preserve them in a condition of suitable
freshness during the brief period of nourishment. The numerous items
composing the ration, consumed in order, one by one, are thus preserved
for some days, notwithstanding that they are corpses.
Imagine, on the other hand, a single item, big enough to furnish the
whole banquet; the conditions would become detestable. Nibbled here and
there, the generous morsel, with its many wounds, would become a fatal
mess of putrescence long before it was finished; it would poison the
grub with the serum resulting from the wounds. A dish of this kind,
single and sumptuous, demands, as a preliminary, the maintenance of
organic life, together with the abolition of all movement, in a word,
paralysis. It also demands, on the consumer’s part, a special art of
eating, an art that respects the more essential and attacks the less
essential by degrees, as the Scoliæ and Spheges [41] have shown us. For
reasons which escape me, the Pelopæus is unacquainted with the
paralysers’ art, nor does her larva know how a bulky piece of game may
be consumed without danger. She is therefore very happily inspired when
she provides her family with a large number of small game. The
restricted capacity of the store-houses is not the main motive that
dictates her choice: there would be nothing to deter the potter from
making bigger pickle-jars, were there any advantage to be gained. The
preservation of dead victuals is of the foremost consequence; and, to
achieve it within the brief limits of the feeding-period, the huntress
fills her bag with none but the smaller Spiders.
Better still: if I open cells that have been recently closed, I always
find the egg, not on the surface of the heap, on the last Spider
supplied, but right at the bottom, on the piece earliest in date, the
first to be stored. Whenever I witness the start of the provisioning, I
see the egg lying on the single Spider wherewith the cell is then
provided. There is no exception to the rule: the Pelopæus at once fixes
her egg on the first morsel served up, before resuming the chase to
complete the ration. The Bembeces deal similarly with their dead Flies:
the first carcase stowed away receives the egg.
But this conformity of habits goes no farther. The Bembeces continue to
bring provisions day by day, as the larva increases in size, a method
easily practised in a burrow closed with a mere screen of loose sand,
through which the mother passes easily in either direction. The
Pelopæus has not the same facilities of ingress and egress: once the
earthen jar is closed and sealed, she would have, in order to reenter
the cell, to break the lid, which is now dry and would offer a
resistance out of all proportion to the means at the disposal of the
Wasp accustomed to handling fresh mud. Moreover, each of these
laborious burglaries would have to be followed by a rebuilding, which
also would be an arduous task.
It is not therefore the Pelopæus’ practice to feed her offspring day by
day; and the hoard of victuals is completed as swiftly as possible. If
game be not abundant, if the atmospheric conditions be difficult,
several days are required to fill the cell thoroughly. In favourable
weather, an afternoon is sufficient. No matter what time the hunting
may take, long or short according to circumstances, the laying of the
egg at the bottom of the cell, on the first piece served, is a happy
device on whose excellence I have already laid stress in my history of
the Odynerus. The victuals provided for a cell fill it to the brim and
are stacked in the order of acquisition, with the Spiders earliest in
date at the bottom and the more recent on the surface. No subsidence,
which would lead to a mixture of fresh game and high, is possible,
because of the game’s long legs, which in most cases scrape against the
walls of the cell with their stiff hairs. The larva, at the bottom of
the heap and, moreover, intent upon the morsel attacked, thus proceeds
from the oldest to the less old and always finds in front of its teeth,
until the end of the meal, victuals that have not had time to spoil by
decomposition.
The egg is laid indifferently upon a large joint or a small, according
to the chances of the first capture. It is white, cylindrical, slightly
curved and measures three millimetres in length, with a diameter of
rather less than one millimetre. [42] The spot that receives it on the
Spider’s body varies hardly at all; it is at the beginning of the
abdomen, towards the side. The new-born larva, as is usual with the
Hunting Wasps, takes its first bite at the point where the pole of the
egg containing the head was fixed. Thus, for its first mouthfuls, it
has the juiciest and tenderest part, the Spider’s plump belly. Next
comes the thorax, abounding in muscular tissues, and lastly the legs,
dry morsels, but not despised. Everything goes down, from the best to
the coarsest; and, when the meal is finished, there is practically
nothing left of the whole heap of Spiders. This life of gluttony lasts
for eight to ten days.
The larva then works at its cocoon, which consists at first of a sack
of pure, perfectly white silk, an extremely delicate sack, affording
little protection to the recluse. This is only a woof, destined to
become a better stuff, not by additional weaving, but by the
application of a special lacquer. The spinner is a worker in oiled
silk.
In the spinning-mills of the carnivorous Wasps, two methods of
manufacture are employed to give the silken fabric greater toughness.
On the one hand, the fabric is encrusted with numerous grains of sand,
which produces an almost mineral shell wherein the silk has no other
function than to serve as a cement for the stony materials. That is how
the Bembeces, the Stizi, the Tachytes and the Palari work. On the other
hand, the larva elaborates in its stomach, in its chylific ventricle, a
liquid varnish which it disgorges into the meshes of a rudimentary
tissue of silk. Directly it trickles into the web, the varnish hardens
and becomes a lacquer of exquisite daintiness. The larva next ejects at
the base of the cocoon, in the form of a hard stercoral plug, the
residue of the chemical process accomplished in its stomach for the
elaboration of the varnish. This method is that of the Spheges, the
Ammophilæ and the Scoliæ, who varnish the inner wrapper of their
multiple cocoons; and of the Crabro-wasps, the Cerceres and the
Philanthi, [43] whose delicate cocoon consists of only a single
thickness.
The Pelopæus adopts this last procedure. When finished, her work is an
amber-yellow fabric suggesting the outer skin of an onion in fineness,
colour, transparency and the rustling sound which it emits when
fingered. Relatively long in comparison with its width, as is demanded
by the capacity of the cell and the slender form of the future insect,
the cocoon is rounded at the top and suddenly truncated at the base,
which is rendered hard and opaque by the stercoral plug, the by-product
of the lacquer-factory.
The hatching-period varies, of course, according to the temperature and
also according to certain conditions which I am not yet in a position
to specify. One cocoon, woven in July, gives birth to the perfect
insect in the course of August, two or three weeks after the larva’s
period of activity; another, dating from August, opens a month later,
in September; a third, no matter what its date of origin during the
summer quarter, goes through the winter and does not burst until the
end of June. By combining the birth-certificates recorded, I seem to
distinguish three generations in the year, generations which are often
but not invariably realized. The first appears at the end of June: this
is the one whose cocoons have gone through the winter; the second is
seen in August and the third in September. So long as the very hot
weather lasts, evolution is rapid: three or four weeks suffice to
complete the Pelopæus’ cycle. When September arrives, the fall in
temperature puts an end to these precocious broods; and the last larvæ
have to wait for the return of the hot weather before they can undergo
their transformation.